The present invention relates to a push button indicating device suitable for a push operating member of passive parts such as a push button switch.
Conventionally, various types of indicating means have been used to indicate an operational position of an operating portion of the passive parts. In a rotary type, the operating portion is generally provided at its outer periphery with a mark such as a projection or a line, so that the operational position may be perceived from a change in an angle of the mark relative to the body of the passive parts. In a sliding type, the operating portion is provided at its part with a mark similar to the above, so that a change in a position of the mark relative to the body of the passive parts may be perceived. In a push type, it is difficult to judge whether the operating portion is in a depressed position or an undepressed position when an operator looks at the operating portion from a front side thereof. Therefore, in a push button switch for example, the operating portion itself or a lamp provided near the operating portion is generally designed to turn on in the depressed position of a push button to thereby indicate an on-state of the push button. An example of this push button switch is disclosed in Japanese Laid-Open Utility Model Publication No. 55-151987 by the common applicant.
FIG. 6 is a sectional view of an essential part of the lighted push button switch disclosed in the above cited reference. The push button switch includes a light transmissible cap 1 made of synthetic resin acting as a push member, a light transmissible indicator plate 2, a front plate 3, an operational member 4, a rotational member 6 having rotary plates 7 and 8, a cover 9, a lamp 10, a coil spring 11, a switch 12, a return spring 13 for the switch 12, an arm 14 and a coil spring 15 for biasing the arm 14 rightward.
The cap 1 is formed with a through-hole 1c a front surface 1a and with a recess 1b just inside the through-hole 1c. As shown in FIG. 7, an illustrated indication for function or kind is formed on an upper half of the front surface 1a.
The indicator plate 2 includes a flat portion 2a engaged with the recess 1b of the cap 1, an projected indicating portion 2b inserted into the through-hole 1c of the cap 1, a support portion 2d formed at right angles to the flat portion 2a and extending along a side wall of the cap 1, and a tongue portion 2i c projected in a L-shape from the end of the support portion 2d. The tongue portion 2c is adapted to abut against the rotary plate 7 or 8 to rotate the same. A distance between the tongue portion 2c and the flat portion 2a is larger than a radius of rotation of the rotary plate 7.
The front plate 3 is formed with an angular cylindrical through-hole 3a and with a projecting portion 3b projecting from an intermediate position of one side surface and extending rearward (leftward as viewed in FIG. 6). The projecting portion 3b is formed with a shoulder portion 3c having an inside recess 3d and an outside recess 3e, and with an engagement portion 3f adapted to engage with the arm 14 in cooperation with the recess 3e.
The operational member 4 is of an angular cylinder to be inserted into the through-hole 3a of the front plate 3. The operational member 4 is formed with an operational arm 4a projecting from a side wall of a rear end portion thereof in such a manner as to be opposed to the shoulder portion 3c of the front plate 3. A partition wall 4c partitioning an opening portion 4b of the operational member 4 into upper and lower opening sections extends from the front end to the substantially central portion of the operational member 4. A side wall of the lower opening section 4pposite the partition wall 4c is cut away to a nearly central position thereof.
The rotational member 6 is of a substantially sectional L-shape such that the rotary plate 7 of a light transmissible material is arranged at right angles to the rotary plate 8 of a light shieldable material. The rotational member 6 is supported by support shafts 6a inserted into a right-angular portion from both sides thereof.
The cover 9 is formed with a recess 9b communicated with the through-hole 3a of the front plate 3, and with a switch mounting hole 9c opposed to the projecting portion 3b of the front plate 3.
The lamp 10 as a light source is fitted with a hole 9a formed through a botton portion of the recess 9b. The cover 9 and the front plate 3 is formed with any suitable connecting means (not shown) such as a screw connecting portion or a snap-in connecting portion to be thereby connected with each other.
The coil spring 11 is located between the recess 3d and the operational arm 4a to normally bias the operational member 4 and prevent undue play.
The push button switch 12 including a self-lock mechanism is provided with a terminal plate 12a and an operational rod 12b. A spring pressure of the coil spring 13 is greater than that of the coil spring 11.
The arm 14 is formed with an engagement portion 14a engaged with the engagement portion 3f of the front plate 3, and is formed with a side plate 14c projecting into the opening portion 4d of the operational member 4 in such a manner as to be stepped up from the engagement portion 14a. The engagement portion 14a is provided at its rear portion with a stopper 14b abuttable against the engagement portion 3f, and is further provided at its rear end with a projection 14e. Side surfaces of the side plate 14c extend to the front side to form lug portions 14f of a small width. The lug portions 14f are formed at their end portions with engagement holes 14d engaged with the support shafts 6a of the rotational member 6. The coil spring 15 serving to bias the arm 14 frontward (rightward) is located between the arm 14 and the recess 3e.
The self-lock mechanism of the switch 12 is such that when the push rod 12b is depressed, it is locked in a depressed position, and is restrained from being returned to an initial position even after a depression force is removed. When the push rod 12b is depressed again, and the depression force is removed, the locked condition is released to let the push rod 12b be returned to the initial position.
The operation of the conventional switch will be set forth below. First, the switch 12 is operated in the following manner. When the cap 1 is depressed, the operational member 4 is moved rearward (leftward as viewed in FIGS. 6 to 10). As shown in FIG. 10, the push rod 12b is fully depressed to be locked, and when the depression force is removed, the push rod 12b is slightly moved reversely, and is retained in the locked position shown in FIG. 9. At this time, a contact provided in the switch 12 is switched on, and is retained in the on-state. Next, when the cap 1 of FIG. 9 is depressed to the position shown in FIG. 10, the push rod 12b locked is unlocked, and when the depression force is removed, the push rod 12b is returned to the initial position shown in FIG. 6.
During the course of the above operation of the switch 12, the indicating position 2b is changed as follows:
In the undepressed position of the cap 1, the indicating portion 2b is opposed to the light shielding rotary plate 8. When the cap 1 is depressed, the tongue portion 2c is separated from the rotary plate 7 to abut against the rotary plate 8. Then, the rotational member 6 starts rotating as shown in FIG. 8. When the cap 1 is further depressed, the rotary plate 7 is rotated to the position opposite to the indicating portion 2b, whereby the indicating portion 2b is brightened by the light emitting through the rotary plate 7. That is, the opening portion 4b of the operational member 4 is partitioned substantially equally into upper and lower halves by the partition wall 4c, and the rotational member 6 is located in the lower half of the opening portion 4b. Accordingly, an upper half of the front surface 1f cap 1 is illuminated by the light from the lamp 10, thereby allowing the illustrated indication to be perceived, while a lower half of the front surface 1a, that is, the indicating portion 2b is lightened according to the depressed position of the cap 1, that is, the operational condition of the push button switch 12.
However, in the push button switch as mentioned above, the lamp 10 is mounted in each of the switches. Therefore, in the cases that like push button switches are arranged, or any other equipment including lighting parts are arranged in association, the number of the lamp 10 is increased to increase costs of parts and an amount of heat generated. As a result, the push button, that is, the cap 1 becomes hot.
To cope with this problem, it is considered that the light sources such as the lamp 10 are located outside the push button switch, and the light from the light sources is guided through a light guiding member to the opening portions 4b and 4d of each of the operational members 4, thereby lighting desired portions. That is, in the prior art employing the light sources located on the back side of the operational members 4 and at the position relatively near the rotational members 6, it is not especially necessary to use the light guiding member. To the contrary, when the light sources are located outside the push button switch, attenuation of the light is remarkable, and accordingly, it is necessary to use the light guiding member to thereby guide the light to the rotational members 6. Thus, the use of the light guiding member enables diffusion of the light to be suppressed at the minimum, thereby guiding the light of high luminance to the rotational members 6. However, in the aforementioned push button switch using the rotational member 6 to transmit or shield the light according to the depressed or undepressed position of the cap 1, if the luminance of the light guided by the light guiding member is intensive, there is a possibility that the light leaks from the periphery of the light shieldable rotary plate 8 of the rotational member 6 to undesirably lighten the indicating portion 2b.
In other words, if the luminance of the light guided by the light guiding member is intensive, the indicating portion 2b is brightly illuminated. Therefore, even in the undepressed position of the cap 1, the indicating portion 2b tends to be brightened. As a result, the undepressed position cannot be visually distinguished from the depressed position.